# README

go-gorm-spanner

Google Cloud Spanner ORM for Go's GORM implementation.

import (
    "gorm.io/gorm"
    _ "github.com/googleapis/go-sql-spanner"

    spannergorm "github.com/googleapis/go-gorm-spanner"
)

db, err := gorm.Open(spannergorm.New(spannergorm.Config{
    DriverName: "spanner",
    DSN:        "projects/PROJECT/instances/INSTANCE/databases/DATABASE",
}), &gorm.Config{PrepareStmt: true})
if err != nil {
    log.Fatal(err)
}

// Print singers with more than 500 likes.
type Singer struct {
    gorm.Model
    Text         string
    Likes        int
}
var singers []Singer
if err := db.Where("likes > ?", 500).Find(&singers).Error; err != nil {
    log.Fatal(err)
}
for s := range singers {
    fmt.Println(s.ID, s.Text)
}

Connection URL Properties

The Cloud Spanner GORM supports the following connection URL properties

Commonly Used Properties

credentials (String): File name for the credentials to use. The connection will use the default credentials of the environment if no credentials file is specified in the connection string. Example: projects/my-project/instances/my-instance/databases/my-db;credentials=/path/to/credentials.json
optimizerVersion (String): Sets the default query optimizer version to use for this connection. See also https://cloud.google.com/spanner/docs/query-optimizer/query-optimizer-versions.

Advanced Properties

minSessions (int): Sets the minimum number of sessions in the backing session pool. Defaults to 100.
maxSessions (int): Sets the maximum number of sessions in the backing session pool. Defaults to 400.
numChannels (int): Sets the number of gRPC channels to use. Defaults to 4.
retryAbortsInternally (boolean): Boolean that indicates whether the connection should automatically retry aborted errors. The default is true.
disableRouteToLeader (boolean): Boolean that indicates if all the requests of type read-write and PDML need to be routed to the leader region. The default is false.
usePlainText (boolean): : Boolean that indicates whether the connection should use plain text communication or not. Set this to true to connect to local mock servers that do not use SSL. Example: projects/test-project/instances/test-instance/databases/test-db;usePlainText=true

Example: projects/my-project/instances/my-instance/databases/my-db;minSessions=100;maxSessions=400;numChannels=4;retryAbortsInternally=true;disableRouteToLeader=false;usePlainText=false

Emulator

See the Google Cloud Spanner Emulator support to learn how to start the emulator. When the emulator has been started and the environment variable has been set, gorm will automatically connect to the emulator instead of Cloud Spanner.

$ gcloud emulators spanner start
$ export SPANNER_EMULATOR_HOST=localhost:9010

Go Versions Supported

Our libraries are compatible with at least the three most recent, major Go releases. They are currently compatible with:

Go 1.21
Go 1.20
Go 1.19

Data Types

Cloud Spanner supports the following data types in combination with gorm.

Cloud Spanner Type	gorm / go type
bool	bool, sql.NullBool
int64	uint, int64, sql.NullInt64
string	string, sql.NullString
json	spanner.NullJSON
float64	float64, sql.NullFloat64
float32	float32, spanner.NullFloat32
numeric	decimal.NullDecimal
timestamp with time zone	time.Time, sql.NullTime
date	datatypes.Date
bytes	[]byte

Limitations

The Cloud Spanner gorm dialect has the following known limitations:

Limitation	Workaround
Nested transactions	Nested transactions and savepoints are not supported. It is therefore recommended to set the configuration option `DisableNestedTransaction: true,`
Locking	Lock clauses (e.g. `clause.Locking{Strength: "UPDATE"}`) are not supported. These are generally speaking also not required, as the default isolation level that is used by Cloud Spanner is serializable.
gorm.Automigrate with interleaved tables	Interleaved tables are supported by the Cloud Spanner `gorm` dialect, but Auto-Migration does not support interleaved tables. It is therefore recommended to create interleaved tables manually.
Cloud Spanner stale reads	Stale reads are not supported by gorm.

For the complete list of the limitations, see the Cloud Spanner GORM limitations.

Nested Transactions

gorm uses savepoints for nested transactions. Savepoints are currently not supported by Cloud Spanner. Nested transactions can therefore not be used with GORM.

Locking

Locking clauses, like clause.Locking{Strength: "UPDATE"}, are not supported. These are generally speaking also not required, as Cloud Spanner uses isolation level serializable for read/write transactions.

Authorization

By default, each API will use Google Application Default Credentials for authorization credentials used in calling the API endpoints. This will allow your application to run in many environments without requiring explicit configuration.

Contributing

Contributions are welcome. Please, see the CONTRIBUTING document for details.

Please note that this project is released with a Contributor Code of Conduct. By participating in this project you agree to abide by its terms. See Contributor Code of Conduct for more information.